Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$114.32	4.818%	$119.8279	$119.83	$119.85	$119.80
Purchase #2	$90.76	12.755%	$102.3364	$102.34	$102.35	$102.30
Purchase #3	$87.26	10.568%	$96.4816	$96.48	$96.50	$96.50
Purchase #4	$224.54	6.237%	$238.5446	$238.54	$238.55	$238.50
Purchase #5	$96.42	4.841%	$101.0877	$101.09	$101.10	$101.10
Purchase #6	$229.59	10.230%	$253.0771	$253.08	$253.10	$253.10
Purchase #7	$103.54	8.420%	$112.2581	$112.26	$112.25	$112.30
7 purchase totals =	$946.43		$1,023.6134	$1,023.62	$1,023.70	$1,023.60